Apparatus and method for converting between linear and rotary motion and systems involving the same

ABSTRACT

An apparatus and a method for converting linear motion to rotary motion are provided. In some embodiments, the apparatus may include a plate having a plurality of connection points and a channel. The apparatus may also include a wobbler having an end that extends along the first axis and a cylindrical body having a second axis that is offset from the first axis by a first angle. The plate may be rotatably connected to the cylindrical body and configured to rotate about the second axis. The apparatus may further include a plurality of flexure assemblies connected to the plurality of connection points of the plate.

TECHNICAL FIELD

The present disclosure generally relates to mechanical linkages. Moreparticularly, the present disclosure relates to apparatuses and methodsfor converting between linear motion and rotary motion and systemsinvolving them.

BACKGROUND

Engines may convert chemical energy or heat energy to kinetic energy.These engines may involve driving a piston in a linear movement tocreate kinetic energy. For example, an internal combustion engine maydrive a piston by igniting fuel, which creates pressure, applying aforce to a piston head to drive the piston through a cylinder. In othertypes of engines, such as heat engines, steam or hot air may createpressure to similarly apply pressure to move a piston. In theseexamples, the piston may move in a linear fashion. Certain application,however, may require a rotational movement. For example, intransportation applications, rotational force may be needed to drivewheels. Other example applications may also utilize rotational movement,such as driving a generator to create electricity.

SUMMARY

Embodiments of the present disclosure may relate to an apparatus forconverting between linear motion and rotary motion about a first axis.In some embodiments, the apparatus may include a plate having aplurality of connection points and a channel, a wobbler having an endthat extends along the first axis and a cylindrical body having a secondaxis that is offset from the first axis by a first angle. The plate maybe rotatably connected to the cylindrical body and configured to rotateabout the second axis. The apparatus may also include a plurality offlexure assemblies connected to the plurality of connection points ofthe plate. The plurality of flexure assemblies may include a firstflexure having a having a first end, a second end, a length extending ina direction parallel to the first axis, a width extending radially fromthe first axis, and a thickness. The plurality of flexure assemblies mayalso include a second flexure having a first end, a second end, a lengthextending in a direction parallel to the first axis, a width extendingtangentially from the first axis, and a thickness. The first end of thefirst flexure may be connected to the first end of the second flexure.The second end of the first flexure may be connected to the plate. Thesecond end of the second flexure may be configured to move in adirection parallel to the first axis.

Embodiments of the present disclosure may include an apparatus forconverting between linear motion and rotary motion about a first axis.In some embodiments, the apparatus may include a plate having at leastone connection point extending outwards and a channel through thecenter. The apparatus may also include a wobbler having an end thatextends along the first axis and at least one cylindrical body having asecond axis that is parallel to the first axis and offset from the firstaxis. The plate may be rotatably connected to the cylindrical body andconfigured to rotate about the second axis. The apparatus may alsoinclude a flexure having a having a first end, a second end, a lengthextending in a direction perpendicular to the second axis, a widthextending parallel to the second axis, and a thickness. The first end ofthe flexure may be connected to a first connection point of the at leastone connection point of the plate. The second end of the flexure may beconfigured to move in a direction perpendicular to the first axis.

Additional features and advantages of the disclosed embodiments will beset forth in part in the following description, and in part will beapparent from the description, or may be learned by practice of theembodiments. The features and advantages of the disclosed embodimentsmay be realized and attained by the elements and combinations set forthin the claims.

It is to be understood that both the foregoing general description andthe following detailed description are examples and explanatory only andare not restrictive of the disclosed embodiments as claimed.

The accompanying drawings constitute a part of this specification. Thedrawings illustrate several embodiments of the present disclosure and,together with the description, serve to explain the principles ofcertain disclosed embodiments as set forth in the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments and various aspects of the present disclosure areillustrated in the following detailed description and the accompanyingfigures. It is noted that, in accordance with standard practice in theindustry, various features are not drawn to scale. In fact, thedimensions of the various features may be arbitrarily increased orreduced for clarity of discussion.

FIG. 1 is a perspective view of an exemplary apparatus for convertingbetween linear motion and rotary motion, according to embodiments of thepresent disclosure.

FIG. 2 is a cross-sectional view of the exemplary apparatus in FIG. 1 .

FIG. 3A is a cross-sectional perspective view of the exemplary apparatusin FIG. 1 .

FIG. 3B is a cross-sectional view of a component that may be used in anexemplary apparatus for converting between linear motion and rotarymotion, according to embodiments of the present disclosure.

FIGS. 4A, 4B, 4C, and 4D are perspective views of various configurationsof the exemplary apparatus in FIG. 1 , according to embodiments of thepresent disclosure.

FIGS. 5A, 5B, 5C, 5D, 5E, and 5F are diagrams of exemplary apparatusesfor converting between linear motion and rotary motion, according toembodiments of the present disclosure.

FIG. 6A is a perspective view of an exemplary apparatus for convertingbetween linear motion and rotary motion, according to embodiments of thepresent disclosure.

FIG. 6B is a perspective view of the exemplary apparatus in FIG. 6A.

FIG. 6C is a side view of the exemplary apparatus in FIG. 6A.

FIG. 6D is a is a perspective view of an exemplary apparatus forconverting between linear motion and rotary motion, according to someembodiments of the present disclosure.

FIGS. 6E and 6F are perspective views of example configurations of theexemplary apparatus shown in FIG. 6D, according to embodiments of thepresent disclosure.

FIG. 7A is a perspective view of an exemplary apparatus for convertingbetween linear motion and rotary motion, according to embodiments of thepresent disclosure.

FIG. 7B is an illustration of the core mechanism of the exemplaryapparatus in FIG. 7A.

FIG. 8 is a schematic representation of a system for converting betweenelectrical and thermal energy, according to some embodiments of thepresent disclosure.

FIG. 9 is a schematic representation of heat pump system, according toembodiments of the present disclosure.

FIG. 10 is a flowchart of an exemplary method for determining drivefrequency, according to embodiments of the present disclosure.

Similar reference numerals refer to similar parts throughout the severalviews of the drawings.

DETAILED DESCRIPTION

The following disclosure provides many different exemplary embodiments,or examples, for implementing different features of the provided subjectmatter. Specific simplified examples of components and arrangements aredescribed below to explain the present disclosure. These are, of course,merely examples and are not intended to be limiting. In addition, thepresent disclosure may repeat reference numerals and/or letters in thevarious examples. This repetition is for the purpose of simplicity andclarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

The terms used in this specification generally have their ordinarymeanings in the art and in the specific context where each term is used.The use of examples in this specification, including examples of anyterms discussed herein, is illustrative only, and in no way limits thescope and meaning of the disclosure or of any exemplified term.Likewise, the present disclosure is not limited to various embodimentsgiven in this specification.

Although the terms “first,” “second,” etc., may be used herein todescribe various elements, these elements should not be limited by theseterms. These terms are used to distinguish one element from another. Forexample, a first element could be termed a second element, and,similarly, a second element could be termed a first element, withoutdeparting from the scope of the embodiments. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Disclosed embodiments may relate to a mechanical linkage to convertbetween rotary and linear motion, which may be referred to as a rotaryflex joint. Disclosed embodiments may reduce the number of moving partsnecessary to convert between linear and rotary motion. For example,rather than using bearings, which can ear out over time, may have addedexpense, may require maintenance (e.g., lubrication), and/or may requirean excessive number of moving parts. For example, bearings may includediscrete bearing rings (e.g., outer and inner), rolling elements (e.g.,rollers, balls), and/or cage parts to secure rolling elements. Disclosedembodiments may address these problems by using one or more flexures.For example, flexures may be used in disclosed embodiments to reduce thenumber of bearings, which may also reduce the number of frictionsurfaces and/or moving parts. Flexures may, for example, temporarilystore necessary shifts as elastic potential energy, as opposed todissipating the energy through friction within bearings.

Disclosed embodiments may operate using rotary motion. Rotary motion mayrotate about an axis and may also be referred to as rotational motional.In some embodiments, the rotational motion may utilize a constantrotational speed and/or torque. In other embodiments, the rotationalmovement may change in speed or torque over time. Example sources ofrotational motion input may include one or more electric motors or otherpower producing rotary sources. Example output (or receiving) devices ofrotational motion may include one or more electrical generators,turbines, compressors, or other power generation or power storagedevices.

Disclosed embodiments may operate using linear motion. In embodimentslinear motion may alternate or oscillate along a given axis over time,which may be referred to as a repetitive linear movement. For example,the motion may move out and back (or up and down) along a line or givenaxis over time. In some embodiments, the motion may oscillate, such asforming a sinusoidal displacement pattern. In other embodiments, themotion may move in other displacement patterns, such as a square wave(or as reasonably square as can be), pulse, triangular wave, sawtoothwave, or other pattern of motion alternating between an extended andunextended positions. Example sources of linear motion input may includepiston-driven engines (e.g., internal-combustion engines, heat engines,Stirling-cycle engines), linear actuators, or other devices thatgenerate a linear motion. Example output (or receiving) devices ofrotational motion may include compressors, cryocoolers, heat engines,water pumps, or other device that may operate using a linear motion asinput.

The rotary flex joint of disclosed embodiments may be bidirectional.Although some embodiments discuss either converting rotary motion torepetitive linear motion or converting repetitive linear motion torotary motion, the rotary flex joint as described in the presentdisclosure may be capable of converting between repetitive linear motionand rotary motion, using either the linear or the rotary motion as thedriving input. For example, disclosed embodiments may receive power froma rotational drive, such as a motor (e.g., an AC or DC electricalmotor). Disclosed embodiments may use that rotational input to producelinear motion, such as an oscillating linear motion. In other examples,disclosed embodiments may receive power from an oscillating linearmotion, such as a piston or actuator (e.g., a Stirling-cycle engine, ahear engine, an internal combustion engine). Disclosed embodiments mayuse the that linear input to provide rotational motion as an output. Inbidirectional embodiments, the same system may be capable of receivinginput from both linear motion and rotational motion.

FIGS. 1 and 2 depict an exemplary assembly for converting between linearand rotational motion, according to embodiments of this disclosure. Theexemplary assembly may be referred to as rotary flex joint 100. In someembodiments, as shown in FIGS. 1 and 2 , rotary flex joint 100 mayinclude a plate 102, a wobbler assembly 104, and a plurality of flexureassemblies 106. The relatively orientation and placement of each of thecomponents may be altered from that shown in FIGS. 1 and 2 consistentwith the descriptions of this disclosure.

In some embodiments, plate 102 may be connected to wobbler assembly 104through one or more bearings 136. As shown, due to an angular differencebetween the axis of the bearing and the axis of the rotational drive, aswobbler assembly 104 rotates, the orientation of the rotational axis ofplate 102 may change, which may form a precession-like movement. Forexample, as the axis of plate 102 rotates about the axis of therotational drive, points along plate 102, although they themselves maynot rotate, may move in an alternating linear motion along the axis ofthe rotational drive. In some embodiments, this linear-to-rotarytranslation in movement may be bidirectional. For example, alternatinglinear movement along one or more points of plate 102 may cause wobblerassembly 104 to rotate.

In some embodiments, plate 102 may have a plurality of connection points108 and a channel 110. For example, connections 108 may include aclamping to attach to a flexure. The clamp may use one or more screws tosecure the flexure to one of connection points 108. Other attachmentmechanisms may be used, such as a bolt, nut, glue, spring, or acombination thereof. Other ways to fix a flexure assemblies 106 to plate102 may be used consistent with disclosed embodiments.

In some embodiments, the plurality of flexure assemblies 106 may beequally spaced about plate 102. For example, as shown, four flexureassemblies 106 may be spaced ninety degrees apart each on plate 102.Although not shown in FIGS. 1 and 2 , in other embodiments, flexureassemblies may be spaced unequally or irregularly. For example, fourflexure assemblies may be spaced about plate 102 with twenty degreesabout the axis normal to the plane of plate 102 separating them (with120 degrees spanning the two bookend flexure assemblies). Still otherpositioning of flexure assemblies relative to plate 102 may be employed,such as irregular spacing. As discussed in this disclosure additionalnumbers of flexure assemblies 106 may be attached to plate 102.

In some embodiments, flexure assembly 106 may include a first flexure112 and a second flexure 114. First flexure 112 may have a first end 120and a second end 122. Second flexure 114 may have a first end 120 and asecond end 122. In some embodiments, both first flexure 112 and secondflexure 114 may have a length extending in a direction parallel to anaxis 124, a width extending in one direction and a thickness. Therefore,both first flexure 112 and second flexure 114 may flex in one directionand be stiff in another direction perpendicular to the first direction.In some embodiments, both first flexure 112 and second flexure 114 maybe flat springs.

In some embodiments, first flexure 112 and second flexure 114 may bemade of any material, both metal and non-metal. In some embodiments,first flexure 112 and second flexure 114 are made of 300 seriesstainless steel (e.g., 304, 304L, 305, etc.), carbon steel (e.g., 1091steel, 1095 steel, etc.), or aluminum alloy. The bending stress of thismaterial may be less than 400 MPa, or less than 300 MPa. In someembodiments, this material may have a high fatigue strength. In someembodiments, first flexure 112 and second flexure 114 are made of a samematerial and have same material properties. In some embodiments, firstflexure 112 and second flexure 114 may be made of different materialsand/or have different material properties and dimensions.

In some embodiments, first end 120 of first flexure 112 may be connectedto first end 120 of second flexure 114; second end 122 of each of firstflexure 112 may be connected to plate 102 at one of the plurality ofconnection points 108; and/or second end 122 of second flexure 114 maybe configured to move in a direction parallel to axis 124. In someembodiments, first flexure 112 and second flexure 114 may be connectedthrough a rocker bar 126. In some embodiments, rocker bar 126 may alsoconnect multiple flexure assemblies 106. In some embodiments, theconnections between first flexure 112 and second flexure 114, betweenfirst flexure 112 and connection points 108, and between second flexure114 and the member configured to linear movement, may include a clamp128. Both rocker bar 126 and clamp 128 may have rounded corners forstress concentration relief purposes.

In some embodiments, first flexure 112 may be configured to deflect in adirection tangential to axis 124 and stiff in a direction radial to axis124; second flexure 114 may be configured to deflect in a directionradial to axis 124 and stiff in a direction tangential to axis 124. Insome embodiments, first flexure 112 and second flexure 114 may deflectin perpendicular directions orthogonal to axis 124. While the first andsecond flexures are shown have a particular axis of deflection in thefigures, in some embodiments the flexures may be oriented such that thedeflection direction of first flexure 112 and second flexure 124 areswapped.

In some embodiments, second end 122 of each second flexure 114 issubjected to a linear repetitive movement of a rod 130. In someembodiments, rod 130 is driven by a Stirling-cycle engine (not shown inFIGS. 1 and 2 .) In some embodiments, the Stirling-cycle engine is afour-cylinder alpha Stirling-cycle engine. In some embodiments, rod 130drives a Stirling-cycle heat pump (not shown in FIGS. 1 and 2 .) In someembodiments, the Stirling-cycle heat pump is a four-cylinder alphaStirling-cycle heat pump.

FIG. 3A depicts a zoom-in cross-sectional perspective view of theexemplary apparatus in FIG. 1 . In some embodiments, channel 110 ofplate 102 may be through the center of plate 102 and along axis 132. Insome embodiments, wobbler assembly 104 may include wobbler 134. Wobbler134 may include a cylindrical body. Plate 102 may be rotatably connectedto wobbler 134 by connecting the inside of channel 110 and the outsideof wobbler 134. Plate 102 therefore may be configured to rotate aboutaxis 132. In some embodiments, plate 102 may be rotatably connected towobbler 134 by at least two bearings 136. In some embodiments, bearings136 may be cylindrical roller bearings, ball bearings, or other devicesthat connect the two components while allowing them to freely rotateabout an axis with reduced or minimal friction.

In some embodiments, wobbler assembly 104 may include shaft 138. Shaft138 may be configured to spin about axis 124. Axis 124 and axis 132 maybe oriented to have a predetermined angle θ relative to each other. Aspreviously discussed, as the plane formed by axis 124 and 132 rotatesabout axis 124, points along plate 102 may oscillate or tilt.

FIG. 3B is a cross-sectional view of a wobbler, according to someembodiments of the present disclosure. In some embodiments, as shown inFIG. 3A-3B, wobbler 134 and shaft 138 are two separate pieces joined bya pin 140. Wobbler 134 has a channel 142. Shaft 138 extends throughchannel 142 of wobbler 134. Rotational and longitudinal movements ofshaft 138 relative to wobbler 134 is restricted by pin 140.

In some embodiments, the repetitive movements of rods 130 aresynchronized so rods are moving up sequentially and radiallysymmetrically. In an example embodiment, rotary flex joint 100 mayinclude an even number of rods 130. In this example, when a first rod130 a moves up, the rod on the opposite side of first rod 130 a may movedown. When first rod 130 a reaches the proximal extreme, the rod on theopposite side of first rod 130 a may reach the distal extreme. Afterfirst rod 130 a reaches the proximal extreme, rod 130 b next to firstrod 130 a may reach the proximal extreme, and the rod on the oppositeside of rod 130 b may reach the distal extreme. As such, rods 130 may besynchronized with the tilt of plate 102, which in turn may drive or maybe driven by the rotation of wobbler 134 relative to plate 102, thus mayconvert to or from a rotary motion around axis 124.

In some embodiments, wobbler assembly 104 may extend along axis 124 andmay be connected to deliver a rotary movement. In some embodiments,wobbler assembly 104 may be connected to drive an electrical generator(not shown).

In some embodiments, wobbler assembly 104 may extend along axis 124 andmay be connected to receive a rotary movement. In some embodiments,wobbler assembly 104 may be connected to be driven by an electricalmotor (not shown).

FIGS. 4A, 4B, 4C, and 4D are perspective views of example states ofoperation of the exemplary apparatus in FIG. 1 . For example, FIGS. 4A,4B, 4C, and 4D may illustrate different working phases of rotary flexjoint 100, according to some embodiments of the present disclosure. Insome exemplary embodiments, as shown in FIGS. 4A-4D, rods 130 a, 103 b,103 c, and 103 d may be driven by phase-offset oscillating linearmotion. For example, rods 130 a, 103 b, 103 c, and 103 d may be drivenby each of the cylinders of a four-cylinder alpha Stirling-cycle engine(not shown). Accordingly, the plurality of connection points 108 mayinclude four corresponding branches 108 a, 108 b, 108 c, and 108 dextending away from channel 110 and the plurality of flexure assemblies106 may include four flexure assemblies 106 a, 106 b, 106 c, and 106 dattached to four connection points 108 a, 108 b, 108 c, and 108 d onfour branches. In this example, matching suffix letter may indicate thatcomponents are on a same branch. For example, flexure assembly 106 a(e.g., first flexure 112 a, second flexure 114 a) may be connected toconnection point 108 a, second end 122 a of second flexure 114 a may beconnected to rod 130 a, etc.

As shown in FIG. 4A, when rod 130 a reaches its upper extreme, the rodon the opposite side, rod 130 c, may reach its lower extreme. At thesame time, rods 130 b and 130 d may be at the middle of their upwardstroke or downward stoke, respectively. To compensate the plate 102tilt, second flexure 114 a may be bent outwards, second flexure 114 c isbent inwards, and first flexures 112 b and 112 d are bent toward branch108 a side.

As shown in FIG. 4B, when rod 130 a may be in the middle of its downwardstroke, rod 130 b may reach its upper extreme, the rod on the oppositeside, rod 130 d, may reach its lower extreme, and rod 130 c may be atthe middle of its upward stroke. To compensate the plate 102 tilt inthis position, second flexure 114 b may be bent outwards, second flexure114 d may be bent inwards, and first flexures 112 a and 112 c may bebent toward the side where branch 108 b is located.

As shown in FIG. 4C, when rod 130 b is in the middle of its downwardstroke, rod 130 c may reach its upper extreme, the rod on the oppositeside, rod 130 a, may reach its lower extreme, and rod 130 d may be atthe middle of its upward stroke. To compensate for the tilt of plate 102in this position, second flexure 114 c may be bent outwards, secondflexure 114 a may be bent inwards, and first flexures 112 b and 112 dmay be bent towards the side where branch 108 c is located.

As shown in FIG. 4D, when rod 130 c is in its downward stroke, rod 130 dmay reach its upper extreme, the rod on the opposite side, rod 130 b,may reach its lower extreme, and rod 130 a may be at the middle of itsupward stroke. To compensate for the tilt of plate 102 in this position,second flexure 114 d may be bent outwards, second flexure 114 b may bebent inwards, and first flexures 112 c and 112 a may be bent toward theside where branch 108 d is located.

Although presented as a repetitive linear motion to rotary motionconversion, the exemplary apparatus shown in FIGS. 4A-4D may convert arotary motion to repetitive linear motions. Accordingly, an electricalmotor may be used to drive a four-cylinder alpha Stirling-cycle heatpump or other linear driven device (not shown).

FIGS. 5A, 5B, 5C, 5D, 5E, and 5F illustrate cross-sectional and topviews of example plate designs, according to some exemplary embodimentsof the present disclosure. As previously discussed, plate 102 mayfunction by being connected with any number of rods 130. In someembodiments, rods 130 may be attached to plate 102 using flexureassemblies 106 that are equally spaced about plate 102. In otherembodiments, flexure assemblies may be irregularly spaced, as previouslydiscussed.

FIG. 5A and FIG. 5B depict an exemplary embodiment of assembly 500A(e.g., an embodiment of rotary flex joint 100) where plate 502A includesa single branch 508A, and therefore only one flexure assembly 506A. Aswobbler assembly 504A rotates about shaft axis 524A, connection point508A may tilt up and down. This motion may be accomplished by a linkage(e.g., bearings 536A) that allows plate 502A to remain rotationallyfixed relative to shaft axis 524A. Because plate axis 532A (e.g., theaxis about which the bearings rotate) is offset by angle θ, connectionpoint 508A may tilt up and down (e.g., +/−angle θ degrees) as shaft 538Arotates. Flexure assembly 506A allows this tilting movement to betranslated to a motion of rod 530A that is linear, parallel to shaftaxis 524A.

FIG. 5C and FIG. 5D depict an exemplary embodiment of assembly 500C(e.g., an embodiment of rotary flex joint 100) where plate 502C includestwo branches 508C, and therefore only two of flexure assembly 506C. Aswobbler assembly 504C rotates about shaft axis 524C, connection points508C may tilt up and down. Because connection points 508C are located atopposite sides of plate 502C, they may move in opposite directions. Forexample, connection point 508C on the left side tilts upward, connectionpoint 508C on the right side may tilt downward. This motion may beaccomplished by a linkage (e.g., bearings 536C) that allows plate 502Cto remain rotationally fixed relative to shaft axis 524C. Because plateaxis 532C (e.g., the axis about which the bearings rotate) is offset byangle θ, connection points 508C may tilt up and down (e.g., +/−angle θdegrees) as shaft 538C rotates. Flexure assembly 506C allows thistilting movement to be translated to a motion of rods 530C that islinear, parallel to shaft axis 524C. However, because the motion of eachof connection points 508C may be phase-offset, the linear motion of thecorrespond rod 530C may also be offset by the same phase. Although thetwo connection points 508C are shown as being diametrically opposed(e.g., spaced 180 degrees apart), in some embodiments, the spacingbetween the two connection points 508BC may be less than 180 degrees,which would allow the phase offset of the linear motion of rods 530C tobe offset by the corresponding amount.

FIG. 5E depicts an exemplary embodiment of assembly 500E (e.g., anembodiment of rotary flex joint 100) where plate 502E includes threebranches 508E, and therefore three of flexure assembly 506E. Althoughthe three connection points 508E are shown as being diametricallyopposed (e.g., spaced 120 degrees apart), in some embodiments, thespacing between the three connection points 508E may be less than 120degrees, which would allow the phase offset of the linear motion of rodsconnected to connection points 508E to be offset by the correspondingamount.

FIG. 5F depicts an exemplary embodiment of assembly 500F (e.g., anembodiment of rotary flex joint 100) where plate 502F includes fourbranches 508F, and therefore four of flexure assembly 506F. Although thethree connection points 508F are shown as being diametrically opposed(e.g., spaced 90 degrees apart), in some embodiments, the spacingbetween the four connection points 508F may be less than 90 degrees,which would allow the phase offset of the linear motion of rodsconnected to connection points 508F to be offset by the correspondingamount. The spacing may be set such that a desired phase offset for thelinear motion is achieved.

Although not shown, additional number of connection points andcorresponding flexure assemblies may be used, consistent with disclosedembodiments. For example, 5, 6, 7, 8, 9, 10, or even more numbers ofconnection points and flexure assemblies may be used. Although notshown, the amount of linear motion generated may be controlled byadjusting the angle between the plate axis (e.g., plate axis 132) andthe shaft axis (e.g., shaft axis 124), the distance of the connectionpoint from the plate axis, or both. For example, the angle may beincreased so that the plate (e.g., plate 102) tilts through a largerangle. Additionally, the distance of the connection point from the plateaxis may also increase the stroke length of the resulting linear motion,since the movement of the tilt along the direction of the shaft axisincreases as the distance from the shaft axis increases.

FIGS. 6A, 6B, and 6C depict views of an exemplary apparatus forconverting between linear motion and rotary motion, according to someembodiments of the present disclosure. In some embodiments, rotary flexjoint 200 may be configured to convert between linear motion and rotarymotion. Rotary flex joint 200 may include a plate 202, a wobblerassembly 204, and a flexure 206.

In some embodiments, plate 202 may include at least one connection point208 extending outwards and a channel 210 through the center of plate202. Wobbler assembly 204 may include two offset axes. Wobbler assembly204 may rotate about a first axis 212. Wobbler assembly 204 may includeat least one cylindrical body 214, which may have a second axis 216parallel to and offset from first axis 212.

In some embodiments, flexure 206 may include a first end 218 and asecond end 220, defining a length extending in a direction perpendicularto second axis 216. Flexure 206 may have a width extending parallel tosecond axis 216 and a thickness extending perpendicular to second axis216.

In some embodiments, first end 218 of flexure 206 may be connected to afirst connection point of the at least one connection point 208 of plate202, and second end 220 of flexure 206 may be configured to move in adirection perpendicular to first axis 212.

In some embodiments, as shown in FIGS. 6A-6C, rotary flex joint 200 mayhave multiple plates 202, wobbler assemblies 204, and flexures 206. Themultiple sets of plate, wobbler assembly, and flexure may share a samefirst axis 212 and may be arranged in parallel. For example, plates 202a, 202 b, . . . , 202 n may be arranged in parallel. Each of thoseplates may include cylindrical bodies (e.g., cylindrical body 214) andmay have a second axis 216 in parallel with, but offset from first axis212 and each of their own second axes. The relative offset of eachsecond axis may determine the phase offset of the corresponding linearmotion. Each of plates 202 may include a flexure (e.g., flexure 206).The flexure of each plate may have a length that extends insubstantially in the same direction, which may be perpendicular tosecond axis 216.

In some embodiments, second ends 220 of flexures 206 may be configuredto move or be moved by a linear driver, such as a piston or actuator.For example, second ends 220 of flexures 206 may be driven by aStirling-cycle engine, heat engine, internal combustion engine, or otherlinear power producing device (not shown in FIGS. 6A-6C). In someembodiments, second ends 220 of flexures 206 may be driven by a pistonrod 222 of a Stirling-cycle engine, or by the cylinder body 224 of theStirling-cycle engine. In some embodiments, multiple of wobbler assembly204 may share a single shaft 226 connecting their cylindrical bodies214. Shaft 226 may be disposed with its axis inline with first axis 212,and may be connected to and drive a device receiving rotational input.For example, shaft 226 may drive electrical generator 228 as shown.

FIG. 6D is a is a perspective view of an exemplary apparatus forconverting between linear motion and rotary motion, according to someembodiments of the present disclosure. In some embodiments, flexureassembly 600 may replace plate 202, flexure 206, and piston rod 222.Flexure assembly 600 may be an assembly or manufactured to one singlepiece or multiple pieces.

In some embodiments, flexure assembly 600 may be generally a flatstructure with a thickness. Flexure assembly 600 may have a fixed end602, a piston rod 604, and a plate 606 disposed between fixed end 602and piston rod 604. Each of fixed end 602, piston rod 604, and plate 606may be connected to a beam 608 by a flexure. For example, fixed end 602is connected to beam 608 by flexure 612, piston rod 604 is connected tobeam 608 by flexure 614, plate 606 is connected to beam 608 by flexure618. In some embodiments, flexures 612, 614, 616 are parallel to eachother and at an angle to beam 608. In some embodiments, flexures 612,614, 616 are perpendicular to beam 608. In some embodiments, beam 608may have a higher stiffness than the flexures. In some embodiments,piston rod 604 may move along the longitudinal direction of flexure 614.In some embodiments, plate 606 may mate with cylindrical body 214, wherethe center axis of plate 606 offsets from first axis 212. Therefore,plate 606 and flexure 616 may move along the longitudinal direction offlexure 616. In some embodiments, flexures 612, 614, 616 may deflect ina same direction. Different amount of deflection may accommodate fixedend 602 to remain fixed, piston rod 604 to move linearly withoutrotation, and plate 606 remain engaged with cylindrical body 214.

Flexure assembly 600 may offer the benefit of adjusting the amplitude orrange of linear motion independent of the offset a wobbler. For example,by increasing the distance between flexures 612 and 614, the system mayprovide a larger linear motion with the same rotational input. In someembodiments, an amplification ratio n may be defined as the ratio of thedistance between flexures 612 and 614 to the distance between flexures612 and 616. In some embodiments, when plate 606 is subjected to rotaryinput, the movement along the longitudinal direction of flexure 616 maybe converted to linear movement of flexure 614 and piston rod 604 ntimes amplified. In some embodiments, when piston rod 604 is subjectedto linear movements, plate 606 may move along the longitudinal directionof flexure 606 with amplitude n times reduced.

FIGS. 6E and 6F are perspective view of example configurations of theexemplary apparatus shown in FIG. 6D, according to embodiments of thepresent disclosure. In some embodiments, as shown in FIG. 6E, piston rod610 may have an upward displacement, bending flexure 614 towards fixedend 602. Flexures 612 and 616 bend in the same direction, resultingplate 606 moving slightly upwards. As shown in FIG. 6F, piston rod 610may have an downward displacement, bending flexure 614 away from fixedend 602. Flexures 612 and 616 bend in the same direction, resultingplate 606 moving slightly downwards as well. The offset of center axisof plate 606 and first axis 212 may then translate this repetitivemovement into a rotary movement.

Although described as a linear to rotary conversion, this exemplaryapparatus may also convert rotary to linear. In some embodiments, arotary movement about first axis 212 may cause plate 606 to move up anddown due to the offset of axis. This up and down movement may then beamplified and drive piston rod 604 to have a repetitive linear movement.

FIG. 7A is a perspective view of yet another exemplary apparatus 700A(also referred to as rotary flex joint 700A) for converting betweenlinear motion and rotary motion, according to some embodiments of thepresent disclosure. FIG. 7B is an illustration of an embodiment of coremechanism 700B of exemplary apparatus 700A of FIG. 7A. Apparatus 700Amay be configured to convert between linear motion and rotary motion. Insome embodiments, rotary flex joint 300 may include at least one plate302, at least one wobbler assembly 304, and multiple flexures 306.Apparatus 700A may differ from other embodiments in that the linearmotion may extend in multiple orientations radially about the axis ofrotation.

In some embodiments, each of plate 302 may include a respectiveconnection point 308 and a channel 310 through the center of plate 302.The connection point 308 may extend outwards, radially from the axis ofrotation of the rotary motion. Each wobbler assembly 304 may include twoaxes that are parallel but offset. Each wobbler assembly 304 may rotateabout a same first axis 312. Each wobbler assembly 304 may include acylindrical body 314, which may have its own second axis 316, parallelto and offset from first axis 312. Plate 302 and wobbler assembly 304may be connected and may be configured to allow relative rotary movementabout second axis 316.

In some embodiments, each of flexures 306 may have a first end 318 and asecond end 320, which may define a length extending in a directionperpendicular to first axis 312. Each flexure 306 may have a widthextending parallel to first axis 312 and a thickness. In someembodiments, first end 318 of each flexure 306 may be connected to adifferent connection point 308 of plate 302, and second end 320 of eachflexure 306 may be configured to move in a direction perpendicular tofirst axis 312. In some embodiments, different flexure 306 may have itssecond end 320 moving in a different direction, but all substantiallytowards first axis 312.

As shown in FIG. 7A, rotary flex joint 700A may include multiple plates302 and corresponding wobbler assemblies 304. In some embodiments, thenumber of plates and wobbler assemblies may match. One plate 302 and onewobbler assembly 304 may mate together and connect to multiple flexures306. For each plate 302 and wobbler assembly 304, first axis 312 may beinline or colinear, but second axes 316 may be parallel with an offset.In some embodiments, multiple flexures 306 may be connected to a singleplate 302 and may be equally spaced about first axis 302. In someembodiments, each plate 302 may connect to the same number of flexures306.

In some embodiments, each flexure 306 may have its second end 320connected to and drive (or be driven by) rod 322. Rog 322 may connect toa linear input or output, such as a piston of an internal combustionengine, a heat engine, a Stirling-cycle engine, a cryocooler, a pump, anactuator, or a compressor. These examples are intended to provide anonlimiting illustration of only a portion of the potential input andoutput mechanisms and should not limit the particular application of therotary flex joints described in this disclosure. In some embodiments,rods 322 have repetitive linear movements in a substantially radialdirection perpendicular to axis 312. Similar to rotary flex joint 100,each rod 322 may reach its extremes sequentially. As such, wobblerassembly 304 is driven to rotate about axis 312, converting from linearrepetitive movements of rods 322.

FIG. 8 is a schematic representation of example system 800 forconverting between electricity and thermal energy, according toembodiments. In some embodiments, system 100 may include AC power input802, switch mode power supply 804, motor controller 806, motor/generator808, and heat pump 902. Although system 800, as shown, may suggest thatit is used to convert electrical power to create a temperaturedifferential, in some embodiments, system 100 may generate electricalpower from a thermal differential. For example, heat pump 902 mayoperate as a heat engine, creating mechanical movement that drivesmotor/generator 808 to create electrical power. And in some embodiments,DC (direct current) power generated by motor/generator 808 may beinverted to create AC (alternating current) power.

In some embodiments, AC power input 802 may provide power in the form ofalternating electrical current (e.g., 120 VAC, 240 VAC). AC power input802 is transformed to DC by a switch mode power supply 804. A motorcontroller 806 may control the power input of, and the performance of,motor/generator 808. Although not shown, in some embodiments,motor/generator 808 may drive shaft 138 of a rotary flex joint (e.g.,rotary flex joint 100, rotary flex joint 200, rotary flex joint 700A).In this example, the rotary flex joint can convert the rotational motionto a repetitive linear motion. For example, the linear motion may driverods (e.g., rods 130 of rotary flex joint 100, rods 222 of rotary flexjoint 200, rods 322 of rotary flex joint 700A). The rods may connect todrive pistons of heat pump 902. In some embodiments, heat pump 902 maybe a Stirling-cycle engine, such as a four-cylinder alpha-configurationStirling-cycle engine. Other configurations of Stirling-cycle enginesand other heat engines may be used in system 800, consistent withdisclosed embodiments.

FIG. 9 is a schematic illustration of an exemplary heat pump system 900,according to embodiments of the present disclosure. In some exemplaryembodiments, system 900 may include a heat pump 902, internal heatexchanger 908, external heat exchanger 910, and power supply 920. System900 may use power supply 920 to drive heat pump 902 to cool a workingfluid to provide air conditioning to cool a structure, such as aresidence or commercial building.

In some embodiments, heat pump 902 may be a Stirling-cycle heat pump,running a reversed Stirling cycle to generate a temperaturedifferential. The temperature differential may cool one side of the heatengine while heating another side. Each side may use a working fluid totransfer the heat, or lack thereof, to a heat exchangers. For example,heat pump 902 may include two working fluid cycles (e.g., working fluidcycle 904 and working fluid cycle 906), which may connect heat pump 902to respective heat exchangers. Cycle 904 may circulate cold-side workingfluid between heat pump 902 and an internal heat exchanger 908 on theinside of dwelling. For example, cycle 904 may provide cool workingfluid to an internal heat exchanger to cool an indoor space. Cycle 906may circulate hot-side working fluid between heat pump 902 and anexternal heat exchanger 910 on the outside of dwelling. For example,cycle 906 may allow hot-side working fluid to radiate outdoors, externalto the insulation of the environment that is being cooled. In thisexample where cycle 904 operates on the cold side and cycle 906 operateson the hot side, system 900 may function as an air conditioner. In anembodiment, cycle 904 may operate using the hot side of heat pump 902and cycle 906 may operate on the cold side of heat pump 902. In thisexample embodiment, system 900 may operate as a heater.

FIG. 10 is a flowchart of method 1000 for identifying a drive frequencyfor operating a heat pump, in accordance with embodiments of the presentdisclosure. It is understood that additional operations may be performedbefore, during, and/or after method 1000 depicted in FIG. 10 , and thatsome other processes may only be briefly described herein. Method 1000can be performed using a heat pump and a drive with a controllablefrequency. For example, method 1000 can be implemented using system 800,such as using motor controller 806, motor 808, and/or heat pump 902. Theheat pump may be connected to the motor using one or more of themechanical assemblies disclosed for converting between linear and rotarymotion (e.g., rotary flex joint 100, rotary flex joint 200, rotary flexjoint 300). In this example electricity is used to power a motor todrive a heat pump.

Method 1000 may identify an efficient frequency to operate the heatpump. In some embodiments, an electrical motor may have an adjustablerotational drive frequency. When the electrical motor operates at arotational frequency matching the resonant frequency of the heat pump,the heat pump may operate at maximum efficiency. While a system couldrely on the predetermined frequency to attempt to operate at thisresonant frequency and achieve efficient operation, the resonantfrequency of a heat pump may change over time. For example,environmental factors such as pressure and temperature may affect theresonant frequency. Additionally, while heat pumps are typically sealedsystems, they may experience gradual pressure losses over time, whichmay also affect their resonant frequency. Therefore, it may bebeneficial to periodically determine the resonant frequency of the heatpump to ensure that it the motor driving the heat pump operates.

Heat pumps may be sealed systems with a resonant frequency that may notbe easily adjusted once manufactured. Therefore, it can be difficult totune a heat pump to a particular resonant frequency. The motor orgenerator (e.g., motor/generator 808) connected to a heat pump or heatengine (e.g., heat pump 902) can be tuned to be driven or drive rotarymotion at a particular frequency, such as by using a controller (e.g.,motor controller 806). Method 1000 may identify the particular frequencyof the motor or generator so that it operates at the resonant frequencyof the connected heat pump, allowing the resulting system to operatewith increased efficiency.

In step 1005, method 1000 may begin a motor drive. In some embodiments,a motor controller may initialize and begin operation of a connectedmotor to drive a heat pump. For example, in the context of system 800,motor controller 806 may initiate motor/generator 808 to drive heat pump902.

In step 1010, method 1000 may determine a frequency sweep range. In someembodiments, step 1010 may include a motor controller identifying therange of frequencies with which a connected motor should be driven. Forexample, in the context of system 800, motor controller 806 may identifya rage of frequencies with which to use to sample power output asmotor/generator 808 drives heat pump 902. The range of frequencies maybe fixed, such as a predetermine range of frequencies that are stored innonvolatile memory. In other embodiments, the range of test frequenciesmay be dynamic. For example, motor controller 806 may store the lastfrequency used to drive heat pump 902 and identify a range offrequencies based on an offset (e.g., a predetermined offset above andbelow) that frequency. In still other embodiments, system 800 maydynamically adjust the frequency range to sample consistent withroot-finding algorithms, such as iterative methods (e.g., Newton'smethod, Secant method, Brent's method).

In step 1015, method 1000 may select a frequency. In some embodiments,step 1015 may include select a predetermined initial frequency. In otherembodiments, method 1000 may identify an initial frequency based on therange identified in step 1010. For example, system 800 may select arandom frequency within the determined frequency range, the high-end ofthe range, or the low-end of the range.

In step 1020, method 1000 may determine output at the selectedfrequency. In some embodiments, step 1020 may include determining thepower draw on the motor generator at the selected operating frequency.For example, system 800 may utilize motor controller 806 to determinethe current draw necessary for motor generator 808 to operate at theselected frequency. In some embodiments, system 800 may measure thepower output produced by heat pump 902 in step 1020. For example, system800 may include temperature probes to evaluate the temperaturedifferential of the hot side and cold side of heat pump 902 to determinethe thermal power output. Still other methods of determine the poweroutput at a given drive frequency may be used consistent with thisdisclosure.

In step 1025, method 1000 may determine whether to increment thefrequency. In some embodiments, step 1025 may include system 800evaluating whether power output should be sampled for additionalfrequencies. For example, system 800 may determine whether furtherincrements in the frequency would fall outside the range of frequenciesto sweep (e.g., from step 1010). In other embodiments, system 800 maydetermine that no further sampling should be completed because thesampled power output is increasing, which may indicate that the minimumpower output has already been sampled. For example, system 800 mayevaluate the sampled power output with each iteration and may determinewhether a local minimum has been reached in the plot of power output. Inthe context of dynamic sampling, such as root-finding algorithms, system800 may evaluate whether the results have converged and, if not, whatthe next appropriate sampling frequency should be. Because the number ofsamples that need to be tested to find the efficient operationalfrequency directly corresponds to the time at which it takes method 1000to complete, dynamic root-finding algorithms may be useful to reduce thenumber of iterations required to identify the efficient operatingfrequency for the system. If method 1000 determines that the frequencycan be further incremented (e.g., step 1025, “YES”), method 1000 mayreturn to step 1015. If method 1000 determines that the frequency shouldnot be further incremented (e.g., step 1025, “NO”), method 1000 mayproceed to step 1030.

In step 1030, method 1000 may determine the frequency with the minimumpower output. In some embodiments, step 1030 may include system 800evaluating the test data to verify the drive frequency which resulted inthe minimum power output. In the context of dynamic root-findingalgorithms, system 800, such as motor controller 806, may include aprocessor that validates the root-finding. In the example of a range ofsampled frequencies, motor controller 806 may include a processor thatevaluates the sampling data to determine the drive frequency with thelowest power output. In an example, the evaluation may include selectingthe drive frequency that had the lowest power output. In anotherexample, the evaluation may include fitting a curve to the drivefrequency data to form an equation where power output is a function ofdrive frequency and solving for the minimum of that function.

In step 1035, method 1000 may select a drive frequency. In someembodiments, step 1035 may include system 800 utilizing the selectedfrequency from step 1030 to operate. For example, motor controller 806may control motor/generator 808 to drive heat engine 902 at the selectedfrequency.

While method 1000 is primarily discussed in the context of usingelectrical power to drive a heat engine, method 1000 may be used forpower generation. For example, heat pump 902 may function as a heatengine that converts a temperature differential to kinetic energy (e.g.,a linear movement). This movement may drive a generator (e.g., motorgenerator 808), and system 800 may control the generator to be driven ata particular frequency, consistent with the steps described for method1000.

As an addition or alternative to method 1000, embodiments may includeadjustments to match resonant frequency specific to the context ofgenerating electrical power from a Stirling cycle engine. For example, aStirling cycle engine (e.g., heat pump 902 operating in a powergeneration configuration) may naturally operate at its resonantfrequency when no load is applied. Therefore, disclosed embodiments mayensure the Stirling cycle engine operates at its resonant frequency,which may increase efficiency, by first applying a temperaturedifferential and determining the operating frequency of the enginewithout load. Disclosed embodiments (e.g., system 800) may then controlthe generator (e.g., motor generator 808) to apply the maximum load atwhich the Stirling cycle engine maintains the determined resonantfrequency.

The foregoing descriptions have been presented for purposes ofillustration. They are not exhaustive and are not limited to preciseforms or embodiments disclosed. Modifications and adaptations of theembodiments will be apparent from consideration of the specification andpractice of the disclosed embodiments. For example, the describedimplementations include hardware, but systems and methods consistentwith the present disclosure can be implemented with hardware andsoftware. In addition, while certain components have been described asbeing coupled to one another, such components may be integrated with oneanother or distributed in any suitable fashion.

Moreover, while illustrative embodiments have been described herein, thescope includes any and all embodiments having equivalent elements,modifications, omissions, combinations (e.g., of aspects across variousembodiments), adaptations or alterations based on the presentdisclosure. The elements in the claims are to be interpreted broadlybased on the language employed in the claims and not limited to examplesdescribed in the present specification or during the prosecution of theapplication, which examples are to be construed as nonexclusive.Further, the steps of the disclosed methods can be modified in anymanner, including reordering steps or inserting or deleting steps.

It should be noted that, the relational terms herein such as “first” and“second” are used only to differentiate an entity or operation fromanother entity or operation, and do not require or imply any actualrelationship or sequence between these entities or operations. Moreover,the words “comprising,” “having,” “containing,” and “including,” andother similar forms are intended to be equivalent in meaning and be openended in that an item or items following any one of these words is notmeant to be an exhaustive listing of such item or items, or meant to belimited to only the listed item or items.

The features and advantages of the disclosure are apparent from thedetailed specification, and thus, it is intended that the appendedclaims cover all systems and methods falling within the true spirit andscope of the disclosure. As used herein, the indefinite articles “a” and“an” mean “one or more.” Similarly, the use of a plural term does notnecessarily denote a plurality unless it is unambiguous in the givencontext. Further, since numerous modifications and variations willreadily occur from studying the present disclosure, it is not desired tolimit the disclosure to the exact construction and operation illustratedand described, and accordingly, all suitable modifications andequivalents may be resorted to, falling within the scope of thedisclosure.

As used herein, unless specifically stated otherwise, the terms “and/or”and “or” encompass all possible combinations, except where infeasible.For example, if it is stated that a database may include A or B, then,unless specifically stated otherwise or infeasible, the database mayinclude A, or B, or A and B. As a second example, if it is stated that adatabase may include A, B, or C, then, unless specifically statedotherwise or infeasible, the database may include A, or B, or C, or Aand B, or A and C, or B and C, or A and B and C.

It is appreciated that the above-described embodiments can beimplemented by hardware, or software (program codes), or a combinationof hardware and software. If implemented by software, it may be storedin the above-described computer-readable media. The software, whenexecuted by the processor can perform the disclosed methods. Thecomputing units and other functional units described in this disclosurecan be implemented by hardware, or software, or a combination ofhardware and software. One of ordinary skill in the art will alsounderstand that multiple ones of the above-described modules/units maybe combined as one module/unit, and each of the above-describedmodules/units may be further divided into a plurality ofsub-modules/sub-units.

In the foregoing specification, embodiments have been described withreference to numerous specific details that can vary from implementationto implementation. Certain adaptations and modifications of thedescribed embodiments can be made. Other embodiments can be apparent tothose skilled in the art from consideration of the specification andpractice of the disclosure disclosed herein. It is intended that thespecification and examples be considered as exemplary only, with a truescope and spirit of the disclosure being indicated by the followingclaims. It is also intended that the sequence of steps shown in figuresare only for illustrative purposes and are not intended to be limited toany particular sequence of steps. As such, those skilled in the art canappreciate that these steps can be performed in a different order whileimplementing the same method.

What is claimed is:
 1. An apparatus for converting between linear motionand rotary motion about a first axis, comprising: a plate having aplurality of connection points and a channel; a wobbler having an endthat extends along the first axis and a cylindrical body having a secondaxis that is offset from the first axis by a first angle; wherein theplate is rotatably connected to the cylindrical body and configured torotate about the second axis; a plurality of flexure assembliesconnected to the plurality of connection points of the plate, each ofthe plurality of flexure assemblies comprises: a first flexure having afirst end, a second end, a length extending in a direction parallel tothe first axis, a width extending radially from the first axis, and athickness; and a second flexure having a first end, a second end, alength extending in the direction parallel to the first axis, a widthextending tangentially from the first axis, and a thickness; wherein thefirst flexure and the second flexure are substantially in parallel;wherein the first end of the first flexure is connected to the first endof the second flexure, the second end of the first flexure is connectedto the plate, and the second end of the second flexure is configured tomove in the direction parallel to the first axis.
 2. The apparatus ofclaim 1, wherein the plurality of flexure assemblies are equally spacedabout the plate.
 3. The apparatus of claim 1, wherein the first flexureand the second flexure are flat springs.
 4. The apparatus of claim 1,wherein the first flexure is arranged to deflect in a directiontangential to the first axis.
 5. The apparatus of claim 1, wherein thesecond flexure is arranged to deflect in a direction radial to the firstaxis.
 6. The apparatus of claim 1, wherein the first flexure and thesecond flexure are arranged to deflect in perpendicular directions. 7.The apparatus of claim 6, wherein the perpendicular directions areorthogonal to the first axis.
 8. The apparatus of claim 1, wherein thefirst end of the first flexure is connected to the first end of thesecond flexure through a rocker bar.
 9. The apparatus of claim 8,wherein the first end of the first flexure and the first end of thesecond flexure are both clamped to the rocker bar.
 10. The apparatus ofclaim 1, wherein the plurality of connection points comprise fourbranches extending away from the channel and the plurality of flexureassemblies is four flexure assemblies attached to the four branches. 11.The apparatus of claim 1, wherein the second end of the second flexureis connected to a rod subjected to a linear repetitive movement.
 12. Theapparatus of claim 11, wherein the rod is driven by a Stirling-cycleengine.
 13. The apparatus of claim 12, wherein the end of the wobbler isconnected to an electrical generator.
 14. The apparatus of claim 12,wherein the Stirling-cycle engine is a four-cylinder alphaStirling-cycle engine, the plurality of flexure assemblies comprise fourof the flexure assemblies, and cylinders of the four-cylinder alphaStirling-cycle engine drive the four flexure assemblies.
 15. Theapparatus of claim 11, wherein the end of the wobbler is connected to anelectrical motor.
 16. The apparatus of claim 15, wherein the rod drivesa Stirling-cycle heat pump, and wherein the electrical motor drives theStirling-cycle heat pump at a resonant frequency of the Stirling-cycleheat pump.
 17. The apparatus of claim 11, wherein the second end of thefirst flexure is clamped to the plate.
 18. The apparatus of claim 1,where in the plate is rotatably connected to the cylindrical body by atleast two bearings.
 19. The apparatus of claim 18, where in the twobearings are cylindrical roller bearings.
 20. The apparatus of claim 1,wherein the end of the wobbler is formed by a shaft that extends througha channel through the cylindrical body and rotational movement of theshaft relative to the cylindrical body is restricted by a pin.
 21. Theapparatus of claim 1, wherein the first flexure and the second flexureare separate components.